Thermal relay



Nov. 27, 1934. I H. E. WHITE 1,982,335

, THERMAL RELAY Filegi Nov. 12, 1932 m WLIMMMun!!! WITNESSES: INVENTOR Patented Nov. 27, 1934 PATENT OFFICE THERMAL RELAY Harold E. White, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 12, 1932, Serial No. 642,420

7 Claims.

My invention relates to relays and particularly to time element relays for use in connection with alternating-current apparatus.

It is an object of my invention to provide a novel alternating-current time-element thermal relay of simple and rugged construction.

Another object of my invention is to provide a novel alternating-current thermal relay which shall respond to an alternating current variable with a time element dependent upon some inverse function of the magnitude of the variable.

Other objects of my invention will become evi- 'dent from the following detailed description taken in conjunction with the accompanying drawing, in which Figure 1 is a diagrammatic view in perspective of a relay embodying my invention,

Fig. 2 is a view in elevation of a detail of the relay shown in Fig. 1,

Fig. 3 is a plan view of a modified induction element which may be used in the practice of my invention.

Referring to Fig. 1 in detail, the relay 1 comprises an energizing coil 2 mounted upon the central leg portion 3a of an E-shaped core member 3, of any suitable magnetic material. The core member 3 is preferably of laminated construction and is provided with a lug portion 3b for supporting the movable element of the relay. The relay armature comprises a sheet metal yoke 5, pivotally secured to the lug 31) by means of any suitable fastening element 6, and a copper loop or shading coil 9. The yoke 5 is shaped to'form a dependent crank portion 5b lying below the lug 3b and a pair of arms 50 and 5d extending toward the central leg portion 3a of the core mem- "ber 3.

The central leg portion 3a is cut away to form a pair of shoulders 7 and 8 as may be best seen in Fig, 2. The copper loop or shading coil 9 is secured to the arms 50 and 5c is in such position that it surrounds the upper restricted section of the central leg portion 3a and is freely movable in a substantially vertical direction upon rotation of the yoke member 5 through a limited angle about the fastening member 6.

A pair of magnetic armature elements 10 and 11 are riveted or otherwise suitably secured to the copper loop 9 in positions to engage the shoulders 7 and 8 respectively, when the copper loop 9 is in its lowermost position. The armature elements 10 and 11 may be of any suitable material having relatively high magnetic permeability at ambient temperatures and substantially no magnetic permeability at temperatures of the order of 200 C.

Such materials are known in the art as magnetically reversible materials. A well-known nickel-steel alloy having a nickel content of the order of 36%, which becomes substantially nonmagnetic at 210 C. is suitable for the purpose of my invention. The armature elements 10 and 11 are so disposed with reference to the legs of the core member 3 that they partially bridge the airgaps between the legs when they are in contact with the shoulders 7 and 8.

The relay 1 is provided with suitable contact members 12 controlled by a pair of contact strips 13 and 14 in a manner well understood in the art. The contact strips 13 and 14 are secured to the core member 3 by means of insulating blocks 15 and screws 16 in such a manner that they are insulated from each other and from the core member 3. The contact strip 13 is resilientand normally maintains the contact members 12 in engagement. An insulating block 17 is secured to the end of the contact strip 13 in a position to be engaged by the crank 5b and thereby effect separation of the contact members 12, upon movement of the copper loop 9 in the upward direction.

A pivoted magnetic shunt element 18 is adjustably secured across the open ends of the E-shaped core element 3, to provide an adjustment of the relay air-gaps to thereby vary the reluctance of the magnetic circuit interlinked with the energizing coil 2.

The operation of the apparatus described above may be set forth as follows: Assuming that the energizing coil 2 is energized by alternating current, an alternating current is induced in the copper loop 9 which reacts upon the alternating flux produced in the central leg 3a of the core member 3, to produce a force of repulsion tending to raise the loop 9. However, the magnetic. elements 10 and 11 partially bridge the air-gaps of the core member 3, and thereby divert a suflicient amount of the relay leakage flux to maintain th loop 9 in its lowermost position.

The alternating current in the loop 9 also generates heat which is transmitted directly to the magnetic elements 10 and 11. Upon increase of the alternating current in the coil 2, the FR loss in the loop 9 increases causing a temperature rise in the magnetic elements 10 and 11. When the temperature of the magnetic elements 10 and 11 exceeds 210 0., the elements become substantially non-magnetic, thereby releasing the moving parts of the relay. The repulsive force upon the loop 9 new acts unrestrained to force the loop 9 upward and thereby effect the separation of the contact members 12.

As the time required for the magnetic members 10 and 11 to reach their de-magnetizing temperature is an inverse function of the magnitude of the current in the coil 2, it will be apparent that the relay 1 has inverse time-element characteristics.

By adjusting the magnetic shunt element 18, the ratio of relay fiux to relay current may be varied to thereby vary the relay operating characteristics.

In the modified form of induction element shown in Fig. 3, the copper loop 9a is divided in two parts, which are conductively secured to the magnetic elements 10a and 11a. In this construction,'the alternating current induced in the loop circuit traversesthe magnetic elements 10a and 11a directly. The operation of the apparatus shown in Fig. 3 will otherwise be obvious from that described above in connection with Fig. 1.

I do not intend that the present invention shall be restricted to the specific structural details, arrangement of parts or circuit connections herein set forth as various modifications thereof may be effected without departing from the spirit and scope of my invention. I desire therefore that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In a thermal relay responsive to an alternating electrical condition, a magnetic structure, coil means for energizing said structure, a movable element having actuating means responsive to the magnetic condition of said structure,

magnetic restraining means for said movable element including a member magnetically associated with said structure and thermally responsive to a heat loss derived from said coil means, said member consisting of a material having relatively high magnetic permeability at ambient temperatures and substantially no magnetic permeability at a predetermined temperature above the ambient range, and contact members controlled by said movable element.

2. In a thermal relay responsive to an alternating electrical condition, a magnetic structure, coil means for energizing said structure, a movable element having a closed electric circuit inductively associated with said structure, magnetic restraining means for said movable element including a member magnetically associated with said structure and thermally responsive to a heat loss derived from said 0011 means, said member consisting of a material having relatively high magnetic permeability at ambient temperatures and substantially no magnetic permeability at a predetermined temperature above the ambient range, and contact members controlledby said movable element.

3. In a relay responsive to an alternating electrical condition, a magnetic structure, coil means for energizing said structure, a movable element having a closed secondary coil inductively associated with said structure, magnetic restraining means for said movable element including a member magnetically associated with said structure and subject to the heat loss of said secondary coil,

said member consisting of a material having relatively high magnetic permeability at ambient temperatures and substantially no magnetic permeability at a predetermined temperature above the ambient range, and contact members controlled by said movable element.

4. In a relay responsive to an alternating electrical condition, a magnetic structure, coil means for energizing said structure, a movable element having a closed secondary coil inductively associated with said structure, magnetic restraining means a member magnetically associated with said structure and subject to the heat loss of said secondary coil, said member consisting of a nickel-steel alloy having a nickel content of approximately 36%, and contact members controlled by said movable element.

5. In a thermal relay responsive to an alternating electrical condition, a magnetic structure having an air gap, coil means for energizing said structure, a movable element having actuating means responsive to the magnetic condition of said structure, magnetic restraining means for said movable element including a member magnetically associated with said structure and thermally responsive to a heat loss derived from said coil means, said member consisting of a material having relatively high magnetic permeability at ambient temperatures and substantially no magnetic permeability at a predetermined temperature above the ambient range, contact members controlled by said movable'element and magnetic means associated with said air gap for varying the reluctance of a magnetic circuit of said structure.

6. In an alternating-current thermal relay, a

magneticmember of magnetically reversible ma- -terial thermally responsive to a temperatureconmembers from said initial relative position to said final relative position.

'I. In an'alternating-current thermal relay, a pair of normally-engaged magnetic members including a magnetically-reversible member, means including an energizing coil for exerting a force tending to separate said members and for inductively heating said magnetically reversible member, and contact members operable in response to separation of said members.

HAROLD E. WHITE.

for said movable element including 

